Hardware: 27" 2017 iMac

Connection: Wired

Storage: 1TB SSD

Hi all. I installed Linux Mint on my Mac on an external drive, which was all good fun. But when I went back to boot into MacOS, I got the 🚫 symbol. Booting into recovery mode and running first aid revealed that the disk was corrupted. The only advice it gave was to run first aid in recovery mode, which I was already doing.

Whatever, no big deal, everything important was backed up. So I went ahead and erased the disk using Extended Journaled (I guess APFS is unavailable for Sierra, which is what recovery mode wants to install). I made an installer disk with a later OS but I just received 🚫 again upon selection. Ran first aid again and it passed. Backed out of disk manager and selected install MacOS. Then after about 3 mins. received the error “an error occurred while preparing the installation. Try running this application again”. Tried several more times, receiving the same error every time.

The log reveals even more errors including:

• “Could not find package ref in any source for:” 15 times for different packages such as “base system resources”, “essentials”, “OSInstall” etc.
• No native mechanism to verify InstallESD.dmg
• Couldn’t mount base system dmg! (error code 110)
• IATOOL: Failed the mount outer dmg

I have installed MacOS several times before, including on the same device.